Abstract: With the development of automation technology, the floating crane equipment also starts to use the automatic control system. The frequency converter is used as the core driving part for power balance and speed regulation. This article mainly describes the successful application of the INVT GD800 inverter for floating crane.
Keywords: Floating crane, GD800
1.Floating crane introduction
A floating crane is a floating platform with cranes. It can move cargo anywhere in the port, either by berthing or by moving to an anchorage to divert cargo.
Due to the special environment in offshore construction, there are high requirements for speed control performance. Traditional speed control methods such as wound rotor asynchronous motor rotor series resistance speed regulation, thyristor stator voltage regulation speed regulation and cascade speed regulation, etc. As wound rotor asynchronous motors have collector rings and brushes, they require high cost maintenance.
Its movement route and action can be controlled by a computer in addition to the vfd drive.
2.Best speed control method for floating crane
The inverter is an AC drive for motor, output frequency can be changed. For an AC motor, its rotation speed is close to the synchronous rotation speed determined by the rotation speed of the magnetic field, and the synchronous rotation speed is proportional to the power supply frequency, so changing the frequency also changes the synchronous speed of the motor to adjust the speed.
In the factors such as power frequency, magnetic field strength and slip rate affecting the speed of AC asynchronous motor, the power supply frequency is the key dominant factor. The frequency change speed control mode has good mechanical characteristics, strong anti-disturbance ability, low energy consumption, and adjustment. Wide speed range. Therefore, frequency conversion speed regulation is currently the most perfect speed control method for AC asynchronous motors.
Normally there are 2 control modes for AC motor, V/F control and Vector control.
a) V/F control: The output voltage changes with the output frequency and the compensation output is appropriately taken. Due to the lack of effective means of controlling the flux and torque, the speed accuracy is not high, the torque response is slow, and the dynamic control parameters are poor.
b) Vector control: The essence of vector control is that the AC motor is equivalent to a DC motor, which independently controls the speed and magnetic components. By controlling the rotor flux linkage, and then decomposing the stator current to obtain two components of torque and magnetic field, the orthogonal or decoupled control is achieved through coordinate transformation.
In order to realize the high performance, the customer adopted vector control.
3.Solution of AGV system
The system adopts 4-quadrant GD800 solution, PWM rectifier provide the DC common bus, all the inverter units connected to DC bus.
The following is the system diagram:
4.Advantages of GD800 inverter
GD800 is a frequency converter developed specifically for engineering applications.
Main technical characteristics:
• 380V, 500V, 660V voltage degrees
• Control units and the drives apply optical fiber communication
• Power units apply compatible topology design for an inverter and AFE energy feedback
• Standard STO terminals, to provide the safe parking SS1, safe speed limit function of SLS and to improve system reliability
• Standard cabinet four quadrant products for two-way flow of energy, the energy conservation and environmental protection;
• Unilateral maintenance and compact structure design for the standard cabinet products, to save installation space and to improve convenience of maintenance
• Compatible with Modbus, Profibus-DP and CANopen communication protocols
INVT GD800 series products with excellent performance meet the high requirement of floating crane, it is a perfect solution, which greatly improves the working efficiency, reduces the maintenance cost, the system is stable and reliable, and the operation is more simple.
 《GD800 series operation manual from Shenzhen INVT electric company》